The flavor of the sour cream will be affected by your choice of culture, so if you want a traditional sour cream flavor, then you will need a traditional sour cream culture. Sometimes store-bought sour cream is cultured. However, not all of them are, so you will need to read the label. Store-bought sour cream is generally not a very vigorous culture, so give it a full 24 hours the first time you use it to make homemade sour cream. Cultured buttermilk is a great alternative as the flavor is similar to sour cream. Milk kefir can culture cream, but the yeast part of the culture will change the flavor and consistency of the sour cream to be more like milk kefir. Mesophilic yogurts also have their own, unique flavor. So, they can culture whipping cream, but it won’t taste like store-bought sour cream. Use the sour cream within 3 weeks.